Unless “read-only” is being enforced by hardware (reading from optical media, etc), a compromised sudo user can circumvent anything, and write anywhere. A read-only flag or the root filesystem being mounted from somehwere else are just trivial extra steps in the way.
Improved security != extremely secure, is all I’m saying. There are a lot of things that go into making a system extremely secure, and while an immutable root filesystem may be one of them, it doesn’t do the job all on its own as advertised in this post.
I throw dust jackets away immediately, because I think they’re an abomination and books look and feel better without them. And then I dog-ear the pages because it gives them character.
I must be extra chaotic extra evil.